Branched aromatic polyesters containing cyanuryl nucleus radicals

ABSTRACT

BRANCHED, WHOLLY AROMATIC POLYESTERS OF FORMULA I   2-R2,4-R1,6-R3-S-TRIAZINE   WHEREIN R1, R2 AND R3 EACH CONSIST ESSENTIALLY OF A PLURALITY OF MOIETIES SELECTED FROM THE GROUP HAVING THE FORMULAS II, III, AND IV   -(O-(1,4-PHENYLENE)-CO)A-, -(CO-C6H4-CO)B-,   -(O-C6H4-((X)M-C6H4)N-O)C-   AND WHEREIN X IS   -O-, -SO2-, OR -CO-   M IS O OR 1; N IS O OR 1; A IS 0-40; B IS 0-20; C IS 0-20; AND A+B+CIS 2-40.

"United States Patent Oflice 3,772,250 BRANCHED AROMATIC POLYESTERSCONTAIN- ING CYANURYL NUCLEUS RADICALS James Economy, Eggertsville,Steve G. Cottis, Amherst,

and Bernard E. Nowak, Lancaster, N.Y., assignors to 5 The CarborundumCompany, Niagara Falls, N.Y.

No Drawing. Filed Dec. 8, 1970, Ser. No. 96,234

Int. Cl. C08g 17/02, 17/08 US. Cl. 260-47 CP 11 Claims ABSTRACT OF THEDISCLOSURE Branched, wholly aromatic polyesters of Formula I II N \Q/ t,wherein R R and R each consist essentially of a plurality of moietiesselected from the group having the Formulas II, III, and IV and whereinX is O a -O, or bm is 0 or 1; n is O or 1; a is 0-40; b is 0-20; 0 is0-20; and a+b+c is 2-40.

This invention relates to polyesters, and more particularly to branchedpolyesters wherein branching occurs by virtue of a cyanuryl nucleus towhich linear polyester chains are attached. Still more particularly, thenovel branched polyesters of this invention are substantially whollyaromatic, that is, the linear polyester chains attached to the cyanurylnucleus consist solely of aromatic structural units, although the chainsmay in some instances terminate with an aliphatic end group. Theinvention further relates to methods for the preparation of suchbranched aromatic polyesters, to methods of curing and cross-linkingsuch polyesters, and to cured and crosslinked polyesters producedthereby.

Linear aromatic polyesters are well-known in the art. For example,linear polyesters consisting of repeating poxybenzoyl structural unitsin the polyester chain, sometimes termed p-oxybenzoyl homopolyesters,have been reported. Linear aromatic polyesters have also been reportedwhich consist of recurring, alternating structural units of two types inthe polyester chain: (1) isophthaloyl or terephthaloyl; and (2) paraormeta-dioxyphenylene. Both of these types of linear aromatic polyestersare highly advantageous in that they possess marked thermal stability,especially in contrast to linear polyesters which contain aliphatic aswell as aromatic structural units in the polymer chain. However, bothtypes also have serious disadvantages. For example, p-oxybenzoylhomopolyesters are difiicult to fabricate into desired shapes by mostcon- 3,772,250 Patented Nov. 13, 1973 ventional methods because at hightemperatures they tend to thermally degrade rather than melt, andaccordingly such conventional forming techniques as casting, injectionmolding and extrusion are precluded. The same is true of the otheraforementioned linear aromatic polyesters, especially if the structuralunits are of the para configuration, and while introduction of somestructural units of the meta configuration may improve fabricability, itdoes so at the expense of thermal dimensional stability.

The branched aromatic polyesters of the present invention represent asignificant advance over the prior art linear polyesters. In general,they possess the primary advantage of the linear aromatic polyesters,viz., outstanding thermal stability, while often being more easilyfabricable by virtue of a lower melting or softening point. Moreover,being branched, many polyesters of the invention lend themselves tocross-linking to produce polyesters having superior thermal properties,an advantage not generally possessed by linear polyesters.

According to the present invention there are provided novel branched,wholly aromatic polyesters of Formula I wherein is a cyanuryl nucleusand wherein R R and R each consist essentially of a plurality ofmoieties or structural units selected from the group having the FormulasII, III and IV a, b and 0 being integers representing the total numberof the respective moieties in each of R R and R wherein X is O-,

nisOorlandwhennis 1,m is0or l;aisan integer from 0 to about 40; b is aninteger from 0 to about 20; c is an integer from 0 to about 20; a-|b+cis an integer from 2 to about 40; and the average value of a, b and cfor R R and R is from 2 to about 40. The carbonyl groups of the moietyof Formula III are either para or meta to each other, as isconventionally indicated by the fact that the lines leading to the ringfrom the carbonyl groups intersect sides of the ring rather than beingconnected to specific apices thereof. Accordingly, the dicarbonyl moietyof Formula HI is either isophthaloyl or terephthaloyl, or both withinthe moiety of Formula IV are either para or meta to each V other, as isconventionally indicated, and accordingly the moiety of Formula IV maybe either metaor para-dioxyarylene, or both within the same polyesterchain. When n is equal to 1 in Formula IV, para refers to the 4,4positions and meta refers to the 3,4 or 3,3 positions. In the polyestersof Formula I, the oxy groups of the moieties of Formulas II and IV arelinked to a carbonyl group of a moiety of Formulas II or III or to acarbon atom of the cyanuryl nucleus; the carbonyl groups of the moietiesof Formulas II and III are linked to an oxy group of a moiety ofFormulas II or IV; and the carbon atoms of the cyanuryl nucleus arelinked to an oxy group of a moiety of Formulas II or IV. When a is 0, bis an integer from 1 to about 20- and c is an integer from 1 to about20. When b is 0, a is an integer from 1 to about 40 and c is or 1. Whenb and c are each 0, a is an integer from 2 to about 40.

Preferably, n is equal to 0 in Formula IV, in which case the metaorpara-dioxylarylene moiety is a metaor para-dioxyphenylene moiety ofFormula V tat wherein c has the same significance as described above. Itis also preferable that R R and R each consist essentially of the sametypes of moieties, preferably in approximately the same proportions.

A particularly desirable type of branched aromatic polyesters of FormulaI consists of those polyesters containing the p-oxybenzoyl moiety ofFormula II, either with or without the additional presence of themoieties of Formulas III and IV; i.e., where a is an integer from 1 toabout 40.

It will be apparent that the number of moieties linked together to fromthe polyester chains represented by R R and R must be an integer, asrepresented by a, b and c. However, in many cases it is impractical oreven impossible with available analytical techniques to determine theprecise number of moieties in an individual polyester chain.Accordingly, the number of moieties in the polyester chain is often moreconveniently expressed as the average number of moieties in the threechains, i.e., the average of a, b and c for R R and R In most cases thisaverage is determined as the average value of a, b and c for all of themolecules making up the particular batch of branched polyester beingtested.

In accordance with the invention, low molecular weight branchedpolyesters may be produced having an average of from 2 to about moietiesor structural units in each polyester chain, corresponding to amolecular weight in the range from about 800 to about 2300. Suchbranched polyesters are frequently referred to herein as prepolymers,and their principal utility resides in the fact that their molecularweight may be increased by cross-linking or by extending the length ofthe polyester chains. Many of these prepolymers are fusible. They may beprocessed into a desired physical form and subsequently advanced to ahigh molecular weight polyester having outstanding thermal stability.

Higher molecular weight branched polyesters may also be producedaccording to the invention. It appears that about 40 structural units isthe practical maximum number attainable in the polyester chains,corresponding to a maximum molecular weight from about 14,000 to about25,000. Many of these higher molecular weight polyesters having anaverage polyester chain length of more than about 10 structural units upto about 40 units are useful as thermoplastic molding materials havingexcellent high temperature properties. They may be processed, forexample, by compression molding, impact molding, rani extrusion orplasma spraying to make gaskets,

.Jpearing sleeves, protective coatings, electrical insulating coatingsand the like. Many of the branched polyesters of the invention are alsouseful for the formation of films and fibers, as adhesives, and asmatrices for fiber-reinforced composites.

A variety of procedures and synthetic routes may be employed to producethe branched polyesters of the invention, and they are discussed indetail hereinafter. All involve a reaction or sequence of reactionsbetween suitable reactants which provide the cyanuryl nucleus and thedesired moieties of Formulas -II, III and IV.

The cyanaryl nucleus is suitably provided by a cyanuric halide such ascyanuric bromide, cyanuric iodide, or preferably cyanuric chloride,which is less expensive.

The p-oxybenzoyl moiety of Formula II is suitably provided by anycompound of Formula V1 rvoQ-oom wherein R is lower alkanoyl, benzoyl, orpreferably hydrogen and R is hydrogen, lower alkyl, benzyl, or phenylwherein one or more hydrogens are-replaced by halogen or lower alkyl,phenyl being preferred. The term lower as applied herein to alkyl andalkanoyl refers to a content of from one to six carbon atoms. Examplesof compounds of Formula VI include, among others, p-hydroxybenzoic acid,phenyl p-hydroxybenzoate, p-acetoxybenzoic acid, n-butylp-acetoxybenzoate, n-propyl p-hydroxybenzoate, ethyl p-hydroxybenzoate,phenyl p-acetoxybenzoate, phenyl p-benzoyloxybenzoate, benzylp-hydroxybenzoate, p-cyclohexanecarbonyloxybenzoic acid, cresylp-hydroxybenzoate and m-chlorophenyl p-hydroxybenzoate. Phenylp-hydroxybenzoate is especially preferred, primarily because of itsthermal stability and reactivity.

The isophthaloyl or terephthaloyl moiety of Formula III is suitablyprovided by isophthaloyl chloride or terephthaloyl chloride, or by anycompound of Formula VII (VII) 0 H wherein X, m and n have the meaningdescribed above and R and R independently are lower alkanoyl, benzoyl,or preferably hydrogen. Examples of compounds of Formula VIII include,among others, hydroquinone, resorcinol, m-phenylenediacetate,p-phenylenediacetate, p,pbiphenol, p,p-oxybiphenol,4,4'-dihydroxydiphenyl sulfone, and 4,4' -dihydroxybenzophenone.Hydroquinone and resorcinol are preferred primarily because of theirreactivity and/or lower cost.

(VIII) ether linkages. It is by virtue of such reactions that branchingis accomplished according to the invention. Also, condensation reactionsmay occur as between R, R or R and R OR or 0R whereby the correspondingester is produced as a by-product and the respective moieties linktogether via an ester linkage. It is by virtue of such condensationreactions that polyester chains are elaborated according to theinvention. Ester-ester interchange may, in some cases, occur as betweenpolyester chains of different molecules, whereby the chain lengthsand/or the order of the moieties in the chains may be altered. It isapparent that each polyester chain attached to the cyanuryl nucleus willhave a terminal group, the terminal group of a given polyester chaincorresponding to the specific R R R, R, R or R present in the reactantselected. It is also apparent that, as illustrated in the examples anddescribed elsewhere herein, the composition, number of structural unitsper chain, and molecular weight of the polyesters will depend not onlyupon the reactants selected, but upon the molar ratio thereof, inaccordance with well-known principles.

Many of the desired reactions may be carried out most satisfactorily inthe molten state. Others are preferably carried out in any suitableliquid heat transfer medium, which may be a solvent for one or morereactants and/or reaction products, and which preferably has a highboiling point because some reactions are preferably carried out at arelatively high temperature. Numerous such liquids have been found to besuitable, among which may be mentioned the terphenyls; a eutecticmixture of 73.5% diphenyl oxide and 26.5% diphenyl, commerciallyavailable under the trademark Dowtherm A; mixtures of variouspolychlorinated biphenyls typified by those commercially available underthe trademark Therminol FR; polyaromatic ethers and mixtures thereofsuch as those composed of mixtures of meta and para isomers, havingboiling ranges in excess of 400 C., typified by those commerciallyavailable under the trademark Therminol 77," and partially hydrogenatedterphenyls having boiling ranges in excess of 340 C., typified by thosecommercially available under the trademark Therminol 66.

One particularly desirable class of branched aromatic polyestersaccording to the invention comprises those polyesters of Formula Iwherein each chain attached to the cyanuryl nucleus (i.e., R R and Rconsists essentially of repeating p-oxybenzoyl moieties of Formula II,the average number of structural units in each chain being from 2 toabout 40. Such polyesters correspond to Formula IX Q Q L .l. I L I to Rin Formula VI, thus these polyesters also correspond to Formula Xwherein d, e, f and R have the above-described meanings.

Example 1 illustrates the preparation of a prepolymer of this class ofbranched polyesters. The compound of Formula VI employed is thepreferred compound, phenyl p-hydroxybenzoate, conveniently prepared byreacting phydroxybenzoic acid with phenyl acetate in the presence of HClas a catalyst.

EXAMPLE 1 35.4 kg. (256.5 moles) of p-hydroxybenzoic acid and 43.6 kg.(320 moles) of phenyl acetate are placed into a 1-00 1. round bottomflask equipped with a stirrer, thermometer, distilling head, and acombination nitrogen- HCl inlet tube. The reaction mixture is stirredconstantly under a nitrogen atmosphere throughout the run. The reactionmixture is heated to C., forming a melt, and gaseous HCl is bubbledthrough the melt for 10.5 hours, the temperature being held at 180 C.Phenyl phydroxybenzoate is produced thereby, accompanied by distillationof acetic acid, the HCl serving as a catalyst. The HCl flow isdiscontinued and the temperature of the melt is reduced to 170 C.,whereupon 8.27 kg. (44.8 moles) of cyanuric chloride is added. Thetemperature is held at 170 C. for 3.5 hours, then increased to C. over aperiod of 2 hours. During this stage, some of the phenylp-hydroxybenzoate reacts with all of the cyanuric chloride to producetris(p carbophenoxyphenyl) cyanurate, accompanied by liberation of HCl.The temperature of the melt is then increased from 195 C. to 250 C. overa period of 7 hours and held at 250 C. for 4 hours. During this stage,condensation occurs between the terminal phenoxy groups of thetris(p-carbophenoxyphenyl) cyanurate and the hydroxyl groups of theremaining phenyl p-hydroxybenzoate, accompanied by distillation ofphenol and excess phenyl acetate. The remaining melt is poured intotrays and allowed to cool to room temperature (about 25 C.),solidifying. A yield of 44 kg. is obtained. The product is pulverized,washed with trichloroethylene and extracted with n-heptane in a Soxhletextractor to remove any residual phenol and phenyl acetate, and dried invacuum at 110 C. for 2 hours. The product is a branched polyesterprepolymer corresponding to Formulas :IX and X wherein the average valueof d, e and f is 2 and wherein R is 'phenyl. A substantial proportion ofthe product corresponds to Formulas IX and X wherein each of a, e and fis 2. The product has a melting point of 350 C. as determined bydifferential thermal analysis at a heating rate of 20 C./minute.Saponification of the product and determination of the amount of phenolliberated indicates a phenyl terminal group content of 24.4%,corresponding closely to the theoretical amount of 24.0%. The productcontains 4.1% nitrogen.

Prepolymers such as that produced in Example 1 are fusible. They may beheated with a compound of Formula VI to extend the p-oxybenzoyl chainsand produce a branched, higher molecular weight polyester correspondingto Formulas IX and X with an average chain length of more than about 10up to about 40 p-oxybenzoyl units. such polyesters being useful, forexample, as thermoplastic molding compounds. This process is illustratedin Example 2. 'Such higher molecular weight polyesters may also beprepared directly, as illustrated in Examples 4 and 5.

Alternatively, prepolymers such as that produced in Example 1 may becured by cross-linking by heating with any suitable crosslinking agentat a temperature sufi'iciently high to cause cross-linking, to produce athermoset, cross-linked polyester having outstanding thermal stability.Such cross-linking is illustrated in Example 3. The cross-linkedpolyesters are useful, e.g., as adhesives, films, electrical insulationsand the like. A wide variety of substances may serve as suitablecross-linking agents, including, for example, aromatic dihydroxylcompounds such as resorcinol and hydroquinone; aromatic dicarboxylicacids such as isophthalic acid and terephthalic acid; and low molecularweight polyesters containing aromatic structural units derived from suchdihydroxy compounds or dicarboxylic acids, such as employed in Example3.

(XII) The resulting melt is poured into a stainless steel tray andallowed to cool to room temperature, solidifying. The solid is ground toa powder. A yield of 1037 g. (93% of theory) is obtained. The product isa linear copolyester having a low average molecular weight of about 3600and consisting essentially of three types of moieties or structuralunits, viz, p-oxybenzoyl, isophthaloyl and p-dioxyphenylene. Thestructural units are joined to each other through ester linkages formingpolyester chains, which terminate with a hydroxyl group at each endbecause of the use of a molar excess of hydroquinone. The copolyestermolecules contain about 30 structural units on the average, some of themolecules having Formula XI and the others having Formula XII O (II)EXAMPLE 2 12 g. (about 0.01 mole) of the prepolymer powder produced inExample 1 and 214 g. (1 mole) of phenyl p-hydroxybenzoate are slurriedin 400 g. of a polyaromatic ether heat transfer medium (B.P. above 400C.). The mixture is heated, with stirring and under a nitrogenatmosphere, until a homogeneous liquid forms and further to 320 C. wherethe temperature is held for 10 hours. During this time condensationoccurs, accompanied by distillation of phenol, the p-oxybenzoyl chainsof the branched prepolymer are extended, and the resulting polyesterprecipitates. The reaction mixture is mixed with boiling acetone and thepolyester precipitate is removed by filtration, washed thoroughly withboiling acetone, and dried in air. A yield of 110 g. of polyester powderis obtained. The product is a branched polyester corresponding toFormulas IX and X wherein R is phenyl and the average value of d, e andf is about 30.

EXAMPLE 3 An aromatic polyester useful as a cross-linking agent for theprepolymer of Example 1 is produced as follows. 414 g. (3 moles) ofp-hydroxybenzoic acid, 510 g. (3.75 moles) of phenyl acetate and 954 g.(3 moles) of diphenyl isophthalate are charged into a four-necked resinkettle equipped with a thermometer, stirrer, distilling head and acombination nitrogen-HCI inlet tube. The reaction mixture is stirredconstantly under a nitrogen atmosphere throughout the run. The reactionmixture is heated to 180 C., and HCl is then bubbled through the mixturefor 7 hours, the temperature being held at 180 C. Phenylp-hydroxybenzoate is thereby produced. The HCl flow is discontinued, thereaction mixture is heated to 200 C. at a rate of 10 C./hour, 363 g.(3.3 moles) of hydroquinone is added, and the temperature is furtherincreased to 250 C. over a period of 2.5 hours. The distilling head isthen heated to 190 C. by external heating means to prevent condensationin the distilling head of distillate subsequently to be produced. Thereaction mixture is heated to 320 C. over a period of 6 hours, held at320 C. for 16 hours, heated to 340 C. and held there for 3 hours. Duringthis stage, condensation occurs between the phenyl p-hydroxybenzoate,diphenyl isophthalate and hydroquinone, accompanied by the distillationof phenol. A total of 1127 g. of distillate is collected during theentire run, the distillate containing acetic acid, phenol and the excessphenyl acetate.

wherein g and h are each about 10 on the average.

The linear copolyester .is employed as a cross-linking agent instroke-curing a prepolymer of the invention as follows. 20 g. of thelinear copolyester is blended with 10 g. of the prepolymer powderproduced in Example 1 and the mixture is spread on the surface of a hotplate. The temperature of the hot plate is gradually increased. At about200 C. the mixture forms a clear melt, which is continually agitatedwith a spatula as the temperature continues to rise. When most of thevolatiles have been dissipated, agitation is discontinued and the meltis spread out into a film. As the temperature reaches about 370 C., thematerial solidifies to form a thin, flexible film consisting essentiallyof thermoset cross-linked polyester. The cross-linking presumably occursinitially by virtue of condensation between the terminal hydroxyl groupsof the cross-linking agent and the terminal phenoxy groups of thebranched prepolymer, and subsequently by ester-ester interchangereactions. Various conventional techniques may be employed wherebycross-linking is effected to produce shaped bodies, fiber-reinforcedcomposites and the like.

EXAMPLE 4 414 g. (3 moles) of p-hydroxybenzoic acid, 510 g. (3.75 moles)of phenyl acetate and 1000 g. of a partially hydrogenated terphenyl heattransfer medium (boiling range 340396 C.) are charged into a four-neckedresin kettle equipped as in Example 3. The reaction mixture is stirredconstantly under a nitrogen atmosphere throughout the run. The reactionmixture is heated to 180 C. and HCl is then bubbled through the mixturefor 10 hours, the temperature being held at 180 C. The p-hydroxybenzoicacid is thereby converted to phenyl p-hydroxybenzoate, accompanied bydistillation of acetic acid. The HCl flow is discontinued, thetemperature is reduced to 170 C., and 5.53 g. (0.03 'mole) of cyanuricchloride is added. The reaction mixture is held at 170 C. for 8.5 hours,during which the cyanuric chloride reacts with a small proportion of thephenyl p-hydroxybenzoate to produce tris(p-carbophenoxyphenyl)cyanurate, accompanied by liberation of HCl. Virtually no condensationof the phenyl p-hydroxybenzoate occurs during this stage.

The temperature of the reaction mixture is increased from 170 C. to 320C. at a rate of 10 C./hour and held at 320 C. for 5 hours. Meanwhile,the distilling head is maintained at a temperature of C. to preventcondensation of the distillate in the head. During thisstage,condensation occurs as between the p-oxybenessentially of 1 metaorpara-dioxyarylene moiety of zoyl units attached to the cyanuryl nucleiand the phenyl Formula IV and from 1 to about 40 p-oxybenzoylmolep-hydroxybenzoate and/or. autocondensation products ties of FormulaII. Such polyesters are represented by thereof, chains of repeatingp-oxybenzoyl units linked to Formula I wherein b is O, c is 1, and a isan integer from cyanuryl nuclei thereby being elaborated. The condensa-Ito about 40. tion is accompanied by distillation of phenol. The result-5 One preferred embodiment of such polyesters conteming branchedpolyester forms a precipitate in the reacplates aprepolymer havingFormula XIII (XIII) tion mixture A total of 589 g. of distillatecontaining wherein X, m, n and R have the above-described meanaceticacid, phenol and the excess phenyl acetate is colings, R representingthe terminal groups. Such prepolylected during the entire run. merscorrespond to Formula I wherein b is 0, c is 1, and The resultingpolyester suspension is cooled to room a is 2. They may readily beprepared by condensation of temperature, congealing into a solid mass.The mass is a compound of Formula VI with a compound of Formulaextracted with acetone to remove the heat transfer me- VIII in a molarratio of 2:1 to produce a linear polyester dium and dried in vacuum. Ayield of 330 g. (92.5% of of Formula XIV (XIV) 0 t RmQ-ii-D do... o dort theory) of polyester is obtained, the polyester correspondwherein X,m, n and R have the above-described meaning to Formulas IX and X whereinR is phenyl and ings and R corresponds to the particular R group of thethe average of d, e and f is about 30. The polyester is compound ofFormula VI employed, and then producing essentially the same as the oneproduced in Example 2. branching by reacting the linear polyester withcyanuric Isothermal gravimetric analysis in air at 400 C. resultschloride in a molar ratio of 3:1, as illustrated in Exin a weight lossof only 1.5% /hour. ample 6.

, EXAMPLE 5 A second preferred embodiment of this class of polyesterscontemplates a prepolymer having Formula XV 414 g. (3 moles) ofp-hydroxybenzoic acid, 510 g. (3.75

moles) of phenyl acetate and 1000 g. of a partially hydro- (Xv) jgenated terphenyl heat transfer. medium (bOlilIlg range 340-396 C.) areplaced in a four-necked resin kettle N equipped as in Example 3. Thereaction mixture is stirred RLR constantly under a nitrogen atmospherethroughout the run. The reaction mixture is heated to 180 C. and HClwherem Rm has Formula XVI isthen bubbled through the mixture for 5hours, the (XVI) temperature being held at 180 c. The HCl flow is diso Icontinued, the temperature is reduced to 170 C., 16.6 g (x) g. (0.09mole) of cyanuric chloride is added, and the m temperature is held at170 C. for 8.5 hours. The tem- 5 n i or e 0 0 gfigg g 2 ggl ggg i e s? ifigg i z l g with either end linked to the cyanuryl nucleus carbonincreased to 320 C. over a period of 6 hours, and held atoms and h is atermmal group selected from at 320 C. for 2 hours, the resultingpolyester precipitatthe group conslstmg of lower alkanoyl, z yl andhydroing. A total of 595 g. of distillate is collected during the fprepmyme. t I Where b entire run. 1S 0, c is 1, and a is 1. They mayreadily be prepared The polyester suspension is cooled to C., acetone bycondensanon of a compolind of Formul? VI Wlth a is added, and thepolyester is recovered by filtration, compound of Formula VIII m a molarram) of 1:1 to washed with acetone, extracted with acetone in a SoxhletProduce an ester of Formula XVII extractor, and dried in vacuum at 110C. for 2 hours. V I

A yield of 325 g. (88% of theory) of polyester is obas E tained thePolyester corresponding to Formulas IX and X T- rwherein R is phenyl andthe average of d, e and f is about 11. The polyester tends to flow whensubjected to a n shearing force at about-200 C. Isothermal gravimetricwherein X, m, n, R and R have the above-described analysis in air at 400C. results in a weight loss of 70 meanings and R and R correspond to theparticular R only 1.9% /hour. to R groups of the reactants employed, andthen pro- Another particularly desirable class of branched aroducingbranching by reacting the ester with cyanuric chlornatic polyestersaccording to the invention comprises ride in a molar ratio of 3:1, asillustrated in Example 7. those polyesters of Formula Iwherein eachchain attached It is apparent that R in Formula XV corresponds to to thecyanuryl nucleus (i.e., R R and R consists R or R in Formula XVII.

1 1 A third preferred embodiment contemplates reacting a prepolymer ofFormulas XIII or XV with a molar excess of a compound of Formula VIwhereby condensation occurs and the chains of the branched prepolymerare extended by the addition of repeating p-oxybenzoylmoieties. Thisextension of the chain is analogous to that illustrated in Example 2,and substantially the same conditions may be employed. The polyesters'soproduced contain onl one dioxyarylene moiety in each chain but maycontain up to about 40 p-oxybenzoyl units in each chain, depending uponthe molar ratio of the reactants.

EXAMPLE 6 338 g. (174 moles) of p-phenylene diacetate, 480 g.

(3.48 moles) of p-hydroxybenzoic acid and 500 g. of a polyaromatic etherheat transfer medium (B.P. above 400 C.) are placed in a four-neckedresin kettle equipped as in Example 3. The reaction mixture isconstantly stirred under a nitrogen atmosphere throughout the run. There action mixture is heated to 180 C. and gaseous I-ICl is then bubbledthrough the mixture as a catalyst for hours, the temperature being heldat 180 C. The HCl fiow is then discontinued. The mixture in the resinkettle at this point comprises a suspension of a linear polyester havingFormula XIV wherein R is hydrogen, n is O, and the dioxyarylene moietyis para-dioxyphenylene. The polyester is formed by condensation of thereactants, accompanied by distillation of acetic acid.

To the contents of the resin kettle are added 500 g. of the same heattransfer medium and 107.5 g. (0.583 mole) of cyanuric chloride, and thetemperature of the reaction mixture is held at 180 C. for 8 hours.During this stage the polyester reacts with the cyanuric chloride toproduce a branched polyester prepolymer with the accompanying liberationof HCl, the prepolymer being in suspension.

The mixture is cooled to 80 C., acetone is added, and the mixture isfiltered to recover the product. The product is washed with acetone andis then subjected to extraction with acetone overnight in a Soxhletextractor. The product is dried in vacuum at 110 C. for 2 hours.

A yield of 547 g. (83.8% of theory) of prepolymer powder is obtained.The prepolymer has Formula XIII wherein n is 0, R is hydrogen, and thedioxyarylene moieties are para-dioxyphenylene. The polyester powderforms a clear melt at a temperature of about 340 C.

EXAMPLE 7 828 g. (6 moles) of p-hydroxybenzoic acid and 1020 g. (6.5moles) of phenyl acetate are charged into a fournecked resin kettleequipped as in Example 3. The reaction mixture is stirred constantlyunder a nitrogen atmosphere throughout the run. The reaction mixture isheated to 180 C., and gaseous HCl is then bubbled through the mixturefor 7 hours, the temperature being held at 180 C. Phenylp-hydroxybenzoate is produced thereby. The HCl flow is discontinued and660 g. (6 moles) of hydroquinone is added to the charge. The distillinghead is heated to 180 C., and the reaction mixture is heated from 180 C.to 230 C. at a rate of 10 C./hour, held for 4.5 hours at 230 C., andheated to 240 C. where the temperature is held for 2 hours. Theresulting pasty melt is (XV-III) lO JLO poured while hot into a tray andallowed to cool and solidify, whereupon it is pulverized. A yield of1413 g. is obtained. The'product consists primarily'of ariester, p -hydroxyphenyl p-hydroxybenzoate, having Formula XVII wherein R and R areeach hydrogen, n is 0, and the dioxyarylene moiety ispara-dioxyphenylene. 'The product also contains a linear polyesteridentical to that produced in Example'6. The desired ester is separable''fr omthe linear polyester by virtue of its greater solubility in suchsolvents as acetone. Accordingly, the product is extracted with hotacetone to obtain a solution of the ester and water is added to thesolution to precipitate the ester, which is removed by filtration, driedin vacuum, and cry"- tallized from aqueous isopropyl alcohol. The esteris found to have a melting point of 243 C. upon differential thermalanalysis.

460 g. (2 moles) of the ester and 123 g. (0.67 mole) of cyanuricchloride are suspended in 500 g. of a polyaromatic ether heat transfermedium (B.P. above 400 C.) in a four-necked resin kettle equipped as inExample 3. The mixture is stirred constantly under a nitrogen atmospherethroughout the run. The mixture is heated to 180 C., where thetemperature is held for 10 hours. During this period, the ester reactswith the cyanuric chloride to produce a branched polyester prepolymer,the reaction being accompanied by liberationof I-ICl. The reactionmixture is cooled to C. and acetone is added.thereto. The polyesterproduct is recovered by filtration, washed-with acetone and thenextracted with acetone in a Soxhlet extractor, and dried in vacuum at C.The product is a branched polyester prepolymer corresponding to FormulaXV wherein R is hydrogen and R has the Formula XVI wherein n is 0 andthe dioxyarylene moieties are para-dioxyphenylene.

Prepolymers of Formula XIII may be cured to produce very thermallystable thermoset polyesters. Such curing may be accomplished by heatingthe prepolymer above its melting point, as shown in Example 8.

EXAMPLE 8 5 g. of the branched polyester prepolymer prepared in Example6 is placed on the surface of a hot plate at room temperature and thetemperature is gradually increased to 360 C., the material melting atabout 340 C.

The material is spread out into a film and agitated continuously with aspatula while the temperature is held at 360 C. After about 45 minutes,the material is transformed into a powder as a result of curing, whichpresumably occurs by ester-ester interchange reactions. The product doesnot melt, but decomposes above 450 C., and shows a weight loss in air at400 C. of only 3%/hour. Analysis shows that the product contains 3.0%nitrogen.

Prepolymers of Formula XIII may also be cross-linked by suspending theprepolymer in a suitable liquid heat transfer medium with cyanuricchloride as a cross-linking agent, preferably in an amount of about Amole per mole of prepolymer, and heating to a suitable temperature,preferably at least about ISO-180 C., whereby a cross-linked polyesteris obtained which consists essentially of structural units havingFormula XVIII lei .01 IA Q l wherein X, m and n have the above-describedmeanings. Cross-linking the prepolymer of Example 6 in this mannerproduces a highly cross-linked polyester consisting essentially ofstructural units having Formula XVIII wherein n is and the dioxyarylenemoieties are para-dioxyphenylene.

In the same manner, prepolymers of Formula XV may be cross-linked withcyanuric chloride to produce highly cross-linked and very thermallystable polyesters consisting essentially of structural units havingFormula XIX wherein R has Formula XVI as described above. Crosslinkingthe prepolymer of Example 7 in this manner produces a cross-linkedpolyester consisting essentially of structural units having Formula XIXwherein n is 0 and the dioxyarylene moieties are para-dioxyphenylene.

Another particularly desirable class of branched aromatic polyestersaccording to the invention comprises those polyesters of Formula Iwherein each chain attached to the cyanuryl nucleus (i.e., R R and Rcontains at least one of each of the three moieties of Formulas II, IIIand IV; that is, a, b and c are each at least 1. It is apparent thateach chain must contain at least three structural units, and that theaverage value of a, b and c for R R and R must be at least 3. In thechains of this class of polyesters, the ratio of b to c is approximately1:1. Since the p-oxybenzoyl moiety of Formula II is capable of formingblocks of repeating p-oxybenzoyl units in such chains, the ratio ofa:b:c may be as high as about 10: 1:1, but since the moieties ofFormulas III and IV are capable of forming chains in which such moietiesalternate and form repeating blocks, the ratio of a:b:c may be as low asabout 1:10:10.

Preferably the ratio of a: b:c is about 1:1: 1. In this case, the threemoieties are capable of linking in either of two sequences, represenedby Formulas XX and XXI (XXI) wherein X, m and n have the above-describedmeanings. Accordingly, the polyesters wherein the ratio of azbzc isabout 1:1:1 correspond to Formula XII II) N R"O C-R" a t c ia wherein RR and R independently consist essentially of one or more groups ofFormula XX or one or more groups of Formula XXI with a total number ofp-oxyben'zoyl, dioxyarylene and isophthaloyl or terephthaloyl units offrom 3 to about 40 in each of R R and R Branched polyesters containingeach of the three moieties are conveniently prepared by first condensingreactants of Formulas VI, VII and VIII inv the desired proportions toform a linear copolyester containing the three moieties in the desiredproportions, and then reacting the linear copolyester with about /3 ofits molar amount of cyanuric chloride to produce branching. Example 9illus- 14 trates the preparation of a preferred branched polyestercontaining the three moieties in a ratio of about 1:1:1. Example 10illustrates the preparation of a linear polyester which is branched toproduce a polyester according to the invention, wherein the ratio ofazbzc is about 8:1:1, the chains containing blocks of repeatingp-oxybenzoyl units. EXAMPLE 9 108 g. (003 mole) of the linearcopolyester produced in Example 3, 1.84 g. (0.01 mole) of cyanuricchloride and 100 g. of a partially hydrogenated terphenyl heat transfermedium (boiling range 340-396 C.) are charged into a four-necked resinkettle equipped as in Example 3. The reaction mixture is stirredconstantly under a nitrogen atmosphere throughout the run. The reactionmixture is heated to 180 C. where the temperature is held for 10 hours.During this period, the cyanuric chloride reacts with the copolyester toproduce a branched polyester, HCI being liberated. The resultingpolyester suspension is cooled to room temperature, acetone is added,and the polyester is recovered by filtration, washed with acetone anddried in vacuum at 110 C. for 2 hours. The product is a branchedpolyester having Formula XXII wherein R R and R have the above-describedmeaning; the dicarbonyl moiety is isophthaloyl; the dioxyarylene moietyis p-dioxyphenylene; the ratio of p-oxybenzoyl units to isophthaloylunits to p-dioxyphenylene units is about 1:1:1; and the total number ofp-oxybenzoyl, isophthaloyl and p-dioxyphenylene units in R R and Iaverages about 30.

EXAMPLE 10 138 g. (1 mole) of p-hydroxybenzoic acid, 170 g. (1.25 moles)of phenyl acetate and 39.75 g. (0.125 mole) of diphenyl isophthalate areplaced in a four-necked resin kettle equipped as in Example 3. Themixture is heated to 180 C., and HCl is then bubbled through theresulting melt for 8 hours, during which the temperature is held at 180C. for 6 hours and subsequently at 200 C. for 2 hours. Phenylp-hydroxybenzoate is produced thereby. The HCl fiow is discontinued, and30.6 g. (0.250 mole) of hydroquinone and 500 g. of a polyaromatic etherheat transfer medium (B.P. above 400 C.) are ill added. The temperatureis then raised to 280 C. where it is held for 1 hour, raised to 300 C.where it is held for 2 hours, and raised to 320 C. where it is held for5 hours. The mixture is cooled and acetone is added. The product isrecovered by filtration, washed with acetone, extracted with acetoneovernight in a Soxhlet extractor, and dried in vacuum at C. The productis a linear copolyester consisting essentially of moieties of FormulasII, III and IV in'a ratio of about 8:1:1, where in the moiety of FormulaIII is isophthaloyl and the moiety of Formula IV is para-dioxyphenylene,and the average number of moieties in the copolyester chain is about 10.

The linear copolyester is reacted with about /3 of its molar amount ofcyanuric chloride, in substantial accordance with the procedure ofExample 9, to produce a branched polyester of Formula I wherein themoiety of Formula III is isophthaloyl and the moiety of Formula IV ispara-dioxyphenylene, the ratio of a:b:c is about 8: 1: 1, and a+b+c isabout 10, the polyester chains containing blocks of repeatingp-oxybenzoyl units.

These branched polyesters containing each of the three moieties ofFormulas H, III and IV, as exemplified by those produced in Examples 9and 10, are especially useful as 'thermosetting polyesters, since theymay be cured by heating at a sufficiently high temperatureypreferably 16Such branched polyesters may readily be produced by the condensation ofcompounds of Formulas VII and VIII to form alinear polyester, andreaction of the linear polyester with about 1/3 of the molar amountthereof of cyanuric chloride to produce branching. It will be understoodthat the chains attached to the cyanuric nucleus may have as the finalmoiety an isophthaloyl or terephthaloyl moiety, or a dioxyarylenemoiety. Accordingly, the terminal groups of the chains correspondrespectively to R 'or Not the compound of Formula VII or to R or R ofthe compound of Formula VIII. Therefore, the branched polyesters ofFormula XXIII may correspond to Formulas XXIV or XXV (XXIV) (XXV) l :0LX no '@'li m a new wherein i, j and k independently are integers from 1to about'20 and X, m and n have the above-described meanings. Suchpolyesters are useful, for example, as molding compounds from whichshaped articles may be formed by conventional techniques.

wherein R is a terminal group selected from the group consisting ofhydrogen, lower alkyl, benzyl, phenyl, and phenyl wherein one ormorehydrogens are replaced by halogen or lower alkyl; R is a terminalgroup selected from the group consisting of lower alkanoyl, benzoyl, andhydrogen; and X, m, -n, i, i and k have the above-described meanings.

Example 11 illustratesthe preparation of a prepolymer of this class ofbranched polyesters.

EXAMPLE 11 330 g. (3 moles) of hydroquinone and 974 g. (3 moles) ofdiphenyl isophthalate are placed in a four-necked resin kettle equippedas in Example 3. The reaction mixture is stirred constantly under anitrogen atmosphere throughout the run. The mixture is heated to 250 C.,

forming a melt, and the temperature is maintained at 250 C. for 16hours. During this period the hydroquinone and diphenyl isophthalatereact to produce, as the principal product, p-hydroxyphenyl phenylisophthalate, i.e., an ester of the formula The reaction is accompaniedby distillation of 281 g. (3 moles) of phenol. The product may alsocontain small amounts of unreacted rawlmaterialsand/orhighercondensationproducts, g g r; vThe temperature is r educed't0;vl70 C., 184g. (1 mole) of cyanuric chlorideisadded, and thetemperature is .held at 170 C. for 8 hours. During this period,thereactioli mixture becomes a :yery viscous melt as a result,of thereaction of thexcyanuriochloride and ester toiproduce abranchedpolyester prepolymer.-

1 .The melt is heated to 2103C. to .reduceits viscosity, poured into atray and allowed to cool toroom temperature, solidifying. The'solid isground to a-fine powder. A yield-of 10 93 g. (near ;theoretical),isobtained. The product consists primarily. ofv a branched polyesterprepolymer corresponding-t Formulas XXIII and XXIV wherein n is 0; thedicarbonyl moiety is isophthaloyl; the dioxyarylene moiety ispara-dioxyphenylene; i, j and k are each 1; and R is phenyl. Prepolymerssuch as that produced in Example 11 may be cured by cross-linking toproduce thermoset polyesters having outstanding thermal stability. Thismay be accomplis'l ied'by heating the prepolymer with an aromaticdihydroxyl'c ompound to a"'temperature sufiicient to producecrosslinkingISuch'cross-linking is illustrated in Example 12, thecross-linking agent being the linear copolyester produced in Example 3.

EXAMPLE 12 p a a 4 g. of the linear copolyester produced in Example 3and l g. of the branched polyester prepolymer produced in Example 11 areblended and spread on the surface of a hot plate. The temperature ofthehot plate is gradually increased. At about 250 C. the mixture forms amelt, which is then continually agitated with a spatula as thetemperature continues to rise to 35 0 C. The temperature is held at 350C., with continued agitation. When most of the volatiles have beendissipated, agitation is discontinued and the melt is spread out into afilm. After a total time of about l hour a'thin,'flexible, strong,transparent film is formed consisting essentially of thermosetcross-linked polyester. The cross-linking presumably occurs initially bycondensation between the terminal hydroxyl groups 'of thelinearcopolyeste'r and the terminal phenoxy groups 'of the'bra'richedprepolymer, andlsubse- 1 quently by ester-ester interchangereactions.

Example 13 illustrates the preparation eranotherprepolymer,corresponding to;Formula XXV.

440 g. (4 moles) of hydroquinone and 636 g. (2 moles) of diphenylisophthalate are placed in a four-necked resin kettle equipped as inExample 3. The reaction mixture is stirred constantly under a nitrogenatmosphere throughout the run. The temperature of the distilling head isset at 180 C. and the reaction mixture is heated to 250 C., forming amelt. The temperature of the mixture is held at 250 C. for 7 hours,during which 367 g. of distillate, primarily phenol, is collected. Theresulting melt is poured into a tray and allowed to cool to roomtemperature,

branchedpolyester is prepared from" the ester by mixing the ester in aheat transfer medium, Dowtherm Aflfheating the mixture to 190. 0.. an ga y adding Va mole of cyanuric chloride per mole of the ester. Therebyis produced a prepolymer corresponding to Formula XXV wherein R ishydrogen; n is 0; i, j andk are'each 1; the dicarbonyl moiety is'isophthaloyl; and the dioxyarylene moiety is p-dioxyphenylene.

Prepolymers such as that produced in Example 13 may be cured bycross-linking with additional cyanuric chloride to produce highlycross-linked polyesters possessing marked thermal stability. Thecross-linking may be effected by suspending the prepolymer in a suitableliquid heat transfer medium with about /3 mole of cyanuric chloride permole of prepolymer, and heating to a sufliciently high temperature,preferably about ISO- C. The product is a crosslinked polyesterconsisting essentially of structural units having Formula XXVI L01 V. J

l/ I I n 1 (X)... l owherein X, m and n have the above-describedmeanings. Cross-linking the prepolymer produced in Example 13 in thismanner produces a cross-linked polyester consisting essentially ofstructural units having Formula XXVI wherein n is 0, the dioxyarylenemoieties are p-dioxyphenylene, and the dicarbonyl moieties areisophthaloyl.

Example 14 illustrates the preparation of a branched polyester whereinthe chains consist essentially of alternating moieties of Formulas IIIand IV.

EXAMPLE 14 954 g. (3 moles) of diphenyl isophthalate, 363 g. (33 moles)of hydroquinone, and 1000 g. of a partially hydrogenated terphenyl heattransfer medium (boiling range 340-396 C.) are placed in a four-neckedresin'kettle equipped as in Example 3. The reaction mixture is stirredconstantly under a nitrogen atmosphere throughout the run. The mixtureisheated to 250 C.,then heated from 250 C. to300 C. at a rate of 5C./hour, and finally held at 300 C. until approximately the theoreticalamount of phenol (564 g.) for coinpletecondensation has distilled oif(about 10 hours). The product of the condensation reaction is a linearpolyester'corresponding to the forwherein the average value of pis about10. The polyester chains terminate at each end with a dioxyphenylenemoiety by virtue of the molar excess of hydroquinone employed,

the extent of such excess regulating the average valueof p..

The temperature is reduced to 180 C., 18.4 g. (0.1 mole) of cyanuricchloride isadded, and the temperature is maintained. at 180 C. for 10hours, during which the cyanuric chloride and linear copolyester reactto produce a branched polyester, HCl being liberated. The resultingbranched polyester suspension is cooled to 80 C and acetone is added.The polyester isremoved by. filtration, washed with acetone, and driedin vacuum at 110, C. for 2 hours. The product is a branched polyestercorrespond ing to Formulas XXIII and XXV wherein nis the aver.- age ofi, j and k is about the dicarbonyl moietyis iso phthaloyl; thedioxyarylene moiety is p-dioxyphenylene; and R is hydrogen.

While the invention has been described herein with reference to certainexamples and preferred embodiments, it is to be understood that variouschanges and modifications may be made by those skilled in the artwithout departing from the concept of the invention, the scope of whichis to be determined by reference to the following claims.

We claim:

1. A branched aromatic polyester of the formula RL-CJ \CR1 wherein R Rand R each consist essentially of substituent(s) selected from the groupconsisting of O O a; 4;.

mixtures of H and mixtures of II and mixtures of III and IV, andmixtures of II, III and IV, wherein X is O,

are linked'to 'an oxy group II or IV, a, the number of moieties of Himthe branched aromatic polyester, is from 0 to about 40, b, the number ofmoieties of III in said polyester is from 0 to abo'ut 20, c, the numberof moieties of Formula IV in' said polyester is from 0 to about 20 thesum of a, b, and'c, is an integer from 2 'to about 40, R R 'and'R end interminal group (s) selected from the group consisting of hydroxyl, loweralkoxy, benzoxy, phenoxy and phenox'y wherein atleast one hydrogen isreplaced by halogen or lower alkyl, when the end moiety is'III' or thecarbonyl portion of II is at the end, and end in terminal group(s)selected from the group consisting of hydrogen, lower alkanoyl" andbenzoyl, when the end group moiety is IV or the 0 portion of II is atthe end.

2. A branched aromatic polyester as set forth in claim 1 wherein n is 0.

3. A branched aromatic polyester as set forth in claim 1 wherein R Rand. R each consist essentially of the same types of moieties-inapproximately the same proportions.

4. A branched aromatic polyester as set forth in claim 1 wherein a is aninteger from 1 to about 40.

5. A branched aromatic polyester as set forth in claim 2 wherein a is aninteger from 1 to about 40.

6. A branched aromatic polyester as set forth in claim 3 wherein a is aninteger from 1 to about 40.

7. A branched aromatic polyester as set forth in claim 1 of the formulaCLL E o I B wherein R represents a terminal group and is selected fromthe group consisting of hydrogen, lower alkyl,

benzyl, phenyl and phenyl wherein at least one hydrogen is replaced byhalogen or loweralkyl and d, e, and f are independent integers from 2 toabout 40.

8. A branched aromatic polyester as set forth in claim 7 wherein R isphenyl.

9. A branched aromatic polyester prepolymer as set forth in claim 7wherein d, e, and 7'' independently are integers from 2 to about 10.

10. A branched aromatic polyester prepolymer as set forth in claim 9wherein R is phenyl.

11. A branched aromatic polyester prepolymer as set forth in claim 10wherein each of d, e and f is 2.

References Cited 7 UNITED STATES PATENTS 3,050,496 8/1962 DAleliozen-45.4 3,047,532 7/1962 DAlelio 260--45.4 3,536,664 10/ 1970Picklesimer 26047 3,637,595 1972 Cottis et al 26047 LESTER L. LEE,Primary Examiner US. Cl. X.'R.

1l7161 K; 161 -231; 260-47 CZ, 248 SC, 873

